“This is my take on the SUI version of the Flat4 Dynamic driver IEMs from Ocharaku of Japan , and is taken from my review on earphonia.com .
Ocharaku Flat-4 SUI – In Ear Tech Is Driven Further Forward
by Takeanidea
Flat-4 Sui Ocharaku Earphone
SOUND SIGNATURE 8.5/10
BUILD QUALITY 7/10
VALUE 8/10
PROS
Bass in the realms of a full sized
Sub and mid bass punch and...” --Takeanidea

The Ocharaku Flat4-Kaede
The name Flat4 is derived from the description "Full-range 2-Element 4-Way Effect."
According to the company website this 4-way effect is as follows:
1st effect
Placement of opposed elements reduces mechanical vibration due to anti-resonance.
2nd effect
Twin element parallel drive improves sound pressure sensitivity of low to middle frequency sound.
3rd...